At almost every turn lately, Donald Trump has tried to get under Jeb Bush's skin.
In interviews and on social media, Trump relentlessly needles and mocks Bush, almost to the exclusion of his many other rivals in the Republican presidential field.
Ronald Reagan used to refer to what he called the 11th Commandment — Thou shalt not speak ill of any Republican. But as he has done often during this campaign season, Trump is playing by his own set of rules.